I. Field of the Invention
This invention relates generally to a power tool and more specifically to a power hammer which may be utilized for driving posts, drilling in rock and concrete, forming metal and similar heavy duty applications.
II. Description of the Prior Art
Various designs for power impact tools are described in the prior art. Generally, prior art devices incorporate a reciprocally mounted, spring biased hammer element which is lifted by a rotating cam against the force of the spring and suddenly permitted to drop by virtue of an abrupt shoulder formed in the cam profile. Examples of such arrangements are set forth in the Kollock U.S. Pat. No. 1,712,456; the Grutzbach U.S. Pat. No. 1,798,082; the Sheldon U.S. Pat. No. 2,501,542; the Gibson U.S. Pat. No. 2,646,100 and the Morishita et al U.S. Pat. No. 3,448,817. In each of the foregoing designs, the cam element is offset from the longitudinal axis of the impact hammer which is a serious disadvantage in that undue stress is placed upon the bearings supporting the cam for rotation. This, in turn, leads to frequent breakdown and costly repairs. Then too, the offset arrangement of the cam with respect to the reciprocating hammer tends to produce noxious vibrations resulting in discomfort to the operator and fatigue.
In the design of the present invention, the hammer displacing cam is concentrically positioned about the housing containing the elongated hammer element rather than being offset therefrom. It has been found that this design approach considerably reduces vibrations and also considerably reduces wear on the bearings supporting the cam for rotation.
The design of the power hammer of the present invention also utilizes a unique anvil assembly arrangement which is mounted on the same housing used to contain the reciprocating hammer element. The anvil element is arranged to accept a variety of tools such as chisel bits, striking heads, etc. and is arranged for limited travel upon being impacted by the hammer element. Further, cushioning means are disposed between the anvil element and the housing to further reduce noxious vibration during use.
It is accordingly the principal object of the present invention to provide a new and improved design for a power impact tool.
Another object of the invention is to provide a power impact tool in which a cam operated hammer element is concentrically mounted with respect to the cam.
Another object of the invention is to provide an impact tool which may normally be driven from an electric motor, but which may be simply converted to operate from a non-electric source of rotary power such that the tool may be used in locations where electricity may not be available.